The header <__armlib.h> defines a number of useful ARM specific functions.

Interrupt functions
__ARMLIB_enableIRQ Enable IRQ interrupts.
__ARMLIB_disableIRQ Disable IRQ interrupts.
__ARMLIB_isrEnableIRQ Re-enable IRQ interrupts from within an IRQ ISR.
__ARMLIB_isrDisableIRQ Re-disable IRQ interrupts from within an IRQ ISR.
__ARMLIB_enableFIQ Enable FIQ interrupts.
__ARMLIB_disableFIQ Disable FIQ interrupts.
Debug I/O functions
__ARMLIB_commTX Send a word of data down the ARM debug communications channel.
__ARMLIB_commRX Read a word of data from the ARM debug communications channel.
__ARMLIB_runCommPortServer Serve ARMCPS commands from the ARM's debug communications channel.
Miscellaneous Functions
__ARMLIB_crc32 Compute a CRC-32 checksum of a block of data.